What you just show is just that the BMS is working properly both overvoltage and undervoltage. Thanks for the test, now i know this cheap BMS is working.
you said it! Don't or never use cheap BMS's. I had some from china when I first started my DIY power wall. The bms were a let down. Since then I knew it was of paramount importance to get the quality bms. Its not cheap but the batteries are more important, expensive and delicate.
The BMS is not faulty. All the numbers are within its STATED specifications. These little BMS is for small hobbyist project and not for professional use. Lifepo4 battery are much more rugged that lithium ion and can tolerate a bit of overcharge and over discharge without any significant harm
One big mistake people make is not programming their charger or inverter to operate within the specifications of the BMS. Under normal operating conditions, the BMS should not have to do anything.
@@DannyBokma sure, but all I'm getting at is if my BMS shut off every time the battery was full, it would shut the system down. Likewise when empty. For optimal performance you don't want to hit those limits.
@@benssolarandbattery A BMS for solar should have separate paths for charge and discharge so charging can be stopped while Load can still be supplied. Also if used as you mentioned that absorption and float charge will still degrade the battery as Lithium batteries do not like that. This type of BMS is designed for applications where you only charge or only discharge not both at the same time like for example in a power tool or for an e-Bike (tho this sort of BMS for an eBike will be a bad idea as you need warning before motor cuts off).
I fully agree, on the other hand, you may leave charger in Li-Ion mode by accident or short battery by accident. LFPs are relatively save, but shorting LiPo by accident is serious hazard.
Batrium is expensive, but that would be my first choice of a good BMS. Daly programmable BMS, coming directly from the company you purchase the batteries from is my second option. Other BMS are not available to me in Pakistan, so didn't bother looking at them. Most people on different forums often go for "budget" builds. My issue is that with budget builds, there are greater chances of failures happening that can ruin the inverter or the batteries. Both expensive items. If you are still short by $300~$1,200 dollars to get bms, wires, circuit breakers. Than wait for the money and get good items. Once the system is setup, no one really goes and checked it every few days, much less every few hours after a few months. At the top of the charge, there is a nearly 5% cross of the threshold. At the discharge, there is a nearly 11.5% cross. Thank you for the videos.
@@shinosg-wiz4619 scroll down to balancing power, support.batrium.com/article/127-watchmon-comparison456 Depending on which model you get, you get different rates. In larger systems, it takes longer to balance. The balancing is done passively. You don't need massive amounts of amps to keep on flowing to balance. You just need to do it with small charge over time. I am not knowledgeable enough at the moment to recommend one system over the other or their pros and cons in specific details. I prefer batrium if you are looking to expand your battery backup in the future. If you want to keep the same setup for a few years to come, I prefer Daly bms. I have not used any bms so far, but hope, this is just my opinion on the matter.
@@asderven thank you for the link. Yeah I remembered right. At best 2.2ah. Batrium is made for serious cells (or for those with a good budget lol!) Not for these blue ones because these have generally bigger differences between them compared to way more expensive cells made in Europe.
@@shinosg-wiz4619 blue cells = LiFePo4 cells with aluminum casing. The older ones had harder plastic casing like the winston cells. The blue ones are smaller in size relatively and weigh less as well. As for the quality, if you buy them from a good seller, the blue cells are amazing. Most of these are produced in China, most people just resell them by putting on their own logo at times. If you check out the forums at second life storage, people have tested all kinds of cells quite well. You can read their reviews to make up your mind as well. Glad to help.
I think you’re trying to theorize the use of the BMS differently. The BMS upper and lower voltage cutoffs is to be there as a fail safe. If you are daily charging and discharging the battery to the point the BMS is kicking in, you’ve got your system setup wrong. The charger and inverter should do the limiting and should be set accordingly.
Usually, this kind of BMS used in inexpensive solar systems, where the load side represented as a simple 12V DC-AC inverter, in this kind of inverters user cannot set low cutoff voltage. Anyway, recorded a video just to let people know what to expect from BMS.
Below 2.0 vdc and above 4.2 vdc damages Lifepo4 cells. For that person that would buy the cheapest BMS, probably bought Grade G cells too, so it’s good enough. Thanks for video.
After having similar experiences with some cheap BMS modules, the only ones I use are programmable. It is not worth the risk. As far as balancing, I have mine on a monthly timer rather than continuous balancing. Good video. Thank you!
@@SolarEngineering Hi, I've use several different types, depending on the pack makeup. I stick to the lipo4. With a 48 volt pack, I like this one. www.ebay.com/itm/2A-Bluetooth-Balancer-Li-ion-Lipo-Lifepo4-LTO-Battery-Active-Equalizer-2-24S-BMS-/124047924872?_trksid=p2349624.m46890.l49292. Sometimes I will not use the BMS and build a simple circuit that I can set precisely and depend. I don't trust these physically small BMS units that say 100 or 200 amps. It is always good to keep an eye out for new things on the market though.
For those using this kinds of BMS, I think it will be fine since its doing its job charging the batteries, it's just the fact that their high and low voltage cutoff is too high and low, well I think the protection they offer is supposedly the last resort protection. What I mean is you need to add a dedicated overcharge and over discharge module to make sure your batteries are safe, and in case any of that fails, then this is where this cheap BMS will be useful, at least they will disconnect your battery at some point😅 not to points where those expensive BMS can do better. But for a less budget, this things works!!
BMS is a last stand safeguard. Ideally it never gets called upon to limit discharge or max charge. The BMS only option is to open connection to inverter/charger which prevents damage but leaves you in a situation that must be resolved manually. However, a charger only limits to overall cell pack voltage so if there is some cell imbalance, one cell may go over voltage during chargng unless BMS detect it and trips off. You should avoid cheap BMS's that do not have adjustable max and min cell supervisory trip voltage adjusment. Cheap BMS's are typically fixed with a poor tolerance or even for wrong type cells like LiPo which have higher overcharge trip voltage points. Another big defiiciency is maximum discharge or charge current claims, even on more expensive BMS's. For competitive reasons they often spec short term surge current as their current rating. It is not uncommon for BMS to only handle a continuous discharge current of less then half their claimed current rating. The MOSFET disconnect devices series resistance may be too high resulting in overheating. Lower series resistance MOSFET switches cost more. Also to be careful of is voltage rating of the BMS for the number series connected cells in the battery array. A 4 cell LiFePO4, '12v' battery should have >20v rated MOSFET cutout switch devices. An eight cell '24v battery should have >30v rated MOSFET switch. A sixteen cell '48v' battery should have >60v rated MOSFET switches. The higher the voltage rating of the MOSFET, for a given series resistance device, the more expensive the MOSFET's are. Low cost 12v self-contained LiFePO4 batteries with intenal BMS often are built with only 20-25v MOSFET's. These are not suitable for series stacking to make 24v or 48v array. Check with manufacturers spec to see what their maximum series stacking capability is. It manf. spec does not state maximum stacking then they likely are not suitable to series stackng batteries. For example, BattleBorn states they are four battery stackable to achieve a 48v system array.
I bought those same batteries from battery hookup. They were all mismatched when I got them. I wired them together in parallel for 2 days to equalize them. Which it seemed to. Then I ran them in series with a Daly bms. The batteries all went back to being unequal. So now I'm waiting for a charger that will top balance them. I hope it will solve the problem. The 40 amp Daly bms does not allow the battery pack to get anywhere near full charge. It's a 12s battery. It should charge to 43v . The bms won't let it charge past 40v.
In addition to what Roland W. said, one has to understand that the LFP is not like a simple bucket that when it first overflows it is full or first seems empty is actually empty. LFP is more like a sponge (or a Resistance/Capacitance network). As I am sure you have noticed in your many excellent experiments, if you charge an LFP to 3.65 volts and then come back some time latter (the longer the better) you will no longer be at 3.65 but, instead, well below it. Likewise, when you reach 2.5 and disconnect, come back later and you will be above 2.5 volts. When the manufacturer specifies 2.5 to 3.65 volts for capacity testing, they mean that one should really have a constant 3.65 and 2.5. True, there is not much charge in these regions but if one expects to duplicate the manufacturer's data one has to follow the same procedure. In any case, the internal resistance of the battery prevents the instantaneous flow of charge throughout the battery so it takes time for the charge to dissipate into the entire battery. The voltage you read at the terminals is localized until the battery has had a chance to reach equilibrium. A BMS which can be set to at a given value to disconnect and reconnect at another value can be set to repeatedly charge (or discharge) the battery until it finally approximates a true 3.65 or 2.5 volts. Your cheap BMS in this video apparently can't do this but, as you know, the chargery BMS's you also have can. Frankly, I really wouldn't worry about your BMS cutting off high as the battery is not entirely at this value, just the area local to the terminals. The lower cutoff voltage seems a bit low but that is just me getting paranoid rather than actual data on the matter. In any case, as Roland said, you are not relying on the BMS to handle everyday affairs but rather the solar charge controller or the inverter. Thus, I think the BMS in the video is probably okay to use if all you need is a bare bones BMS.
@@SolarEngineering Admittedly it is confusing and their are plenty of folks out there who say NEVER go above 3.65 or below 2.5. Looking at Victron's website, they say a high of 4.2 volts and a low of 2.5. As Roland remarked, I have seen others who say the low end is 2 volts. I screwed up on a charge cycle the other day and hit more than 4.2 volts for probably 20 minutes or so and my battery still gave me full capacity on discharge (once I noticed my screw up I immediately put a resistor between the terminals and got down to 3.65 volts). In any case, I am trying to do a lot more research on the battery chemistry so I can try and improve the performance of my system as I seem to have batteries that were never matched. Although they are near spec when I test them one at a time, in combination I only get about 70% of the capacity I should. That is probably due to differences in internal resistance. As you may know, the latest rev of the chargery BMS firmware gives us an estimate of internal resistance but I don't know how accurate it is.
@@SolarEngineering There is actually a very good presentation on the intricate details of lifepo batteries on youtube at ruclips.net/video/QlDd3jkcxoQ/видео.html Mind you it is quite technical. The presenter says that lifepo batteries actually handle overcharge very well but when they do start to fall apart is around 4.3 or 4.4 volts where the electrolyte starts to fail. Mind you, it does not happen all at once. The presenter also said LiFePo batteries are not that sensitive to low end voltage either and mentioned keeping cells above one or two volts. Another good article is found here: www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/ This article says 2 volts for the low end cut off and 4.2 for the high end. What is clear from all this is that it is not like falling off of a cliff. You do have a fair amount of wiggle room and even blowing it usually will not destroy your batteries in one big boom. At equilibrium I think a safe range that will give you long battery life is say 3.05 volts on the low cutoff and 3.38 volts or so for the high cutoff. Those are the voltages I'd like after the batteries sit for a while. I'll know more after a lot of painful additional testing. On other interesting factoid for you. My first batteries were 12 volt (4s) lifepo but I made them from 8 cells with 4 groups of two cells in parallel. I think this is similar to what you have except you have 3 cells in parallel and, of course, you are at 48 volts. What threw me for a loop is that I was only getting 70 - 75% of the capacity I should have gotten. I tried lots of different batteries and moved them around (so one might have been the first cell in one case and the third in another) and I just was not getting what I expected capacity wise. So I blamed the batteries. Then I took several individual cells and tested them by themselves and got around 95% capacity. So then I built a 12 volt battery with 4 individual cells so I had none in parallel and, VIOLA!, I got 96% of the capacity I expected! So there is something about putting the cells in parallel that was causing degraded performance. When I did the parallel experiments I had each group of two parallel cells connected to the next group via one bus bar. However, I have seen recommendations that each group of parallel cells should have a busbar per cell connecting to the next group. So, in my case, my two positives in parallel would each have a bar to the two negatives in parallel in the next group. One might think this is overkill, but I calculated that the busbar resistance is about 25% as much as the cells internal resistance so, MAYBE, I need to repeat the experiment with the parallel cell groups connected to the next group with two busbars. OR, maybe the huge differential voltages I saw (250 - 300 millivolts) at the end of discharge were due to some other weird cell chemistry effect that highly favored one cell in a parallel group over another. Anyway, that difference vanished down to something like 30 millivolts when I took my cells out of parallel configuration. Maybe you can run some tests and see what you get?
Pleaese check the BMS spec, it does state the overcharge detect is 3.75V and overdischarger detect is 2.10v. both working exactly as spec in the video.
I think you get it differently sir. The BMS cutoff charging will be higher because when you charge, the voltage will be lifted up. For how much is depending on how fast you charge relative to C rate. Faster charging, higher voltage lift. Also you can find datasheet of any BMS on the internet or from the seller. I hope you understand.
Those boards may contain only a balancer and eventually short circuit protection, not necessarily under/overvoltage protection. From what I saw most of them are JUST balancers. Yeah, always check if they are what you want them to be.
I have a 12V 100Ah LiFePo4 (internal BMS) driving my boat motor and stupidly just connected a 300W solar panel directly to it. I assumed the BMS would prevent overcharge, and it actually worked fine for several months until I made a long trip and fully discharged it. Since then I can't get it to charge, even though the voltage is 14V. Any idea what happened?
Noticing you are using a discharge graph, if you use a charging voltage graph you would get different results. The open circuit voltage is always different than the measured voltage with large current in/out from the battery.
Those voltages are not going to damage the cells to any real extent with LiFePO4. You can actually charge them to a max of 4.2 and a minimum voltage of 2.0v. It's just that you only have about 1% capacity from 3.5 to 4.2v on the top end and only about 1% capacity from 2.5-2v on the bottom end. 3.7 to 2.3 is going to give you around 98-99% of the maximum capacity of the cell. For long-term solar energy storage staying between 3.45 and 2.8 is a good idea but you should not be relying on the BMS to cut power as the charge controller and inverter should be shutting down before the BMS ever reaches the cutoff voltage. Also as you said, if you are building a large battery bank you should be investing in decent components throughout the entire system.
Hi there, didn't know that LiFePo4 could be charged up to 4.2V, in every spec I just saw 3.6V Agree on BMS responsibility, for me ideal BMS is a BMS that could be configured low/high voltage disconnect. And it should control charge and discharge with relays, I'm using chargery BMS, but it's far from ideal.
@@jec_ecart That is a good cycle to follow, LiFePO4 cells will saturate at 3.5V (actually a little less and no reason to push them harder than needed in most storage conditions) if left long enough but it just takes longer than charging them to 3.65. I generally don't take my cells much below 3.15v since I try to keep them off the bottom of the charge curve so I always have a reserve but 2.6 isn't going to hurt them as long as they are recharged in a timely fashion. We must always remember that calendar aging is going to affect the life of the cells far more than cycling for anyone charging once a day or less.
How about if you have MPPT-type solar charger, there is own limits to the charging max and load cutoff. I think they need to be set first (e.g. 14.6V/10V), and then, if those fails, BMS comes to help you, to protect your batteries againts total disaster. Your cheap BMS in video seems to work correctly if thinking like that. What you think?
you are right with the voltages setup, but still, BMS should be in a range of voltage accepted by the battery. here is the video about my system settings: ruclips.net/video/gFwz2uFpEHE/видео.html
I think it's totally possible. Personally I would pay few extra $ and get something programmable, like this one for example: ruclips.net/video/k8Wkg-tVnx8/видео.html
yeah, I checked Electrodacus, for me, it's not going to work because this BMS only supports up to 8 cells, in my case I have a 16s system. But in general, it looks like good quality BMS. I'm using chargery BMS at this time, but quality is questionable. I just got another BMS (check the latest video), haven't fully tested it yet, but looks promising for small and mid systems. Still in search of good BMS for bigger systems (20kWh+).
I was thinking, not sure whom to ask. What if we get 280ah 12V system. What kind of things will we need to make it work with a desktop? A BMS. I want the batteries to provide power to the desktop 24/7, and get charged by the electricity coming out the wall socket (220V ac, there is a solar on the roof, but the wiring will be painful to bring down from 2~3 floors). When the batteries reach a certain low point, they will start charging up slowly. My desktop usually takes 40W~100W. I don't play games right now or edit videos. In future it will be taking 400W~700W. The main purpose is to stop voltage fluctuations from affecting the power supply. To stop sudden power loss to cause any damage to the pc, or when the electricity comes back.
You'll need 12v280AH pack + BMS, then 12v charger (AC-DC) and 12v DC-AC inverter. I don't know your exact application, but I think something like UPS will work better, because you'll use AC grid power when it's available and DC only when AC grid power is off.
@@SolarEngineering I want to run my computer from the batteries 24/7 (uploading, rendering, number crunching). Computers usually have 12V dc power supplies. I just need something to keep the batteries charged up. I was thinking when batteries hit 3V/cell, they start charging at 0.1C~0.2C (set in the inverter), and when it hits 3.5V/cell, it disconnects. The computer drawing electricity is usually quite low. This way the computer is protected. UPS have sine wave issues that I want to avoid, and the UPS I get here are usually with no settings other than factory settings.
@@SolarEngineering stationary pc, batteries with an inverter. I was thinking, I just need a 2KW inverter for the 1,600 watt power supply, and set it up like I would with a solar system and use a bms as well as surge protectors.
Sir, can you please answer me following questions 1. what is 1C charge rate & 3C discharge rate? 2. I have 12ah lifep04 battery pack with 4s 30Amp bms, so will that bms damage my cells with high current ?
1C rating means that full discharge of the cell from full to empty is going to happen in 1 hour. So on your example of 12Ah pack - 1C rating is going to be 12Amps. (If you pull 12 Amps constant load from pack, it will take 1 hour to discharge it). Formula: C rating = charge(discharge) current / pack capacity in Ah. (Example: 0.2C rating = 2.4A / 12Ah ) Coming back to your questions: 1. 1C = 12A, 3C = 36A 2. BMS is not regulating Amperage going in/from the pack, it's just protecting if the current is too high (some BMS has settings, some programmed from a factory). BMS that we see in this video doesn't have that form of protection, BMS will just melt trying to pass current. The second form of protection is low/high cell voltage, BMS will sense voltage on every cell and if it's over limits, then it will disconnect pack from charge (or load). In the video, we see that high voltage disconnect is too high (3.75V), and if you just going to rely on BMS to protect pack from overcharging, then pack will slowly degrade due to constant overcharge. To answer you 2nd question in short: no BMS will not damage your cells because it's not setting amperage in./out, inverter and charge controller will damage cells if you are going to push it over limits.
@@ankamanirudh8837 I answered your question: "will that bms damage my cells with high current" If you are planning to push more than 1C while charging your cells - it will wear pack faster. Please check cells specification about the max current you can charge it.
@@SolarEngineering So, if incomming current from charge controller was 15amp then bms can easily transfer it to cells right? So, this flow will damage my cells right? So should I need to increase my battery pack to 18ah so that charging current it will be in limits right?
Looks like I should build a "test" battery, perhaps using capacitors for cells, so I can test the BMS without damaging real battery cells, or taking such a long time to charge and discharge.
I recently got another BMS (check latest video on the channel), this BMS looks promising, going to test it soon. Hopefully, this BMS will work as expected, then you don't need to build a test battery.
The harm in a cycle or two is miniscule. According to Wikipedia, they last from 2 2000 to 20 000 cycles. I will assume the biggest factor is how they're used. A full range daily cycle would suggest four to five years, at a minimum, unless you are treating them really badly. I suggest that if you are doing full cycles daily, then you should double or treble the number of strings, that automatically reduces the DoD. I would hope that the solar regulator prevents over charging, that the capacity of the battery presents excessive discharging, and that the choice of matched batteries largely keeps them balanced, leaving the BMS not much to do.
Hi, greetings from Spain. I just have a couple of questions regarding how to charge the LifePO4 battery, I want to build a 12v 100Ah portable battery that will be charged only from 220 ac, I will not be using solar panels for charging. In that case I do not need a MPPT, Can I charge the battery just with a cheap PWM made in China and a 12v power supply from a PC.
The bms is ok. A bms is a protection device and is not meant to be used to charge and discharge the batteries. For example, in a solar system, the solar charge controller is the battery charging device and should be configured to stop charging at an appropriate voltage. For a LiFePO4 battery, I'd recommend no more than 3.5v per cell. For discharging, that is usually an AC inverter and they usually shutoff at about 2.65V per cell.
@@mohamadirfanabdullah5913 I'm not getting your question. Lifepo4 max charging voltage 3.65V per cell. This particular BMS states that it will allow charging up to 14.4V, but it definitely failed.
@@SolarEngineering Who told you that this BMS must cut-off at 3.65 volts? Did you read the manual or *NOT* ? The manual states Over-Voltage cut-off at 3.75 Volts !
I have the exact same BMS I purchased just to protect cells while charging. It did NOT work. Thank God I was monitoring with a Battgo. I noticed one cell hit 3.7V, and I immediately diaconnected the charger. That BMS does not work. Pure garbage and waste of money.
I think a lot of DIY LIFEPO4 users do NOT need a BMS , as long as you stay within the upper and lower " knees" of the charging curve , so for a 12 volt ( 4 cell) LiFEpo4 system that would be minimum voltage 12.6 volt an upper chance voltage 13.6 volt, nominal cell voltage is around 3.3 volt, I'm ve been running my 12 volt/ 200 ah solar system for 4 years now WITHOUT a BMS and ( after initial TOP balancing to 3.65 v per cell) the cells stay between those " knees" in perfect balance, so better No BMS than a cheap BMS, a low power cutoff is already in my inverter,and a rightly programmed solar charger keeps the upper voltage in check, wat IS important is to NEVER " FLOAT" LITHIUM, so after reaching the desired chance voltage( I'm using 13.6 volt/ 3.4 volt per cell) STOP CHARGING, could it be simpler?
. You have no idea what your talking about. A bms is the last line of defense as a safety feature for your battery. You just showed me that that is a good bms.
![Felix "Unfair" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/Oswujxm2Ag0/mqdefault.jpg)
What you just show is just that the BMS is working properly both overvoltage and undervoltage. Thanks for the test, now i know this cheap BMS is working.
you said it! Don't or never use cheap BMS's. I had some from china when I first started my DIY power wall. The bms were a let down. Since then I knew it was of paramount importance to get the quality bms. Its not cheap but the batteries are more important, expensive and delicate.
The BMS is not faulty. All the numbers are within its STATED specifications. These little BMS is for small hobbyist project and not for professional use. Lifepo4 battery are much more rugged that lithium ion and can tolerate a bit of overcharge and over discharge without any significant harm
This BMS is only good for making portable power/solar stations probably and I think it is a suitable one for that kind of purpose.
Thanks! This video was really informative and helpful. I've been trying to figure out what safe limits to keep my cells at.
Glad it was helpful!
One big mistake people make is not programming their charger or inverter to operate within the specifications of the BMS. Under normal operating conditions, the BMS should not have to do anything.
The BMS should protect the battery to keep it within the battery limits, regardless of what the consumers / charger is set to.
@@DannyBokma sure, but all I'm getting at is if my BMS shut off every time the battery was full, it would shut the system down. Likewise when empty. For optimal performance you don't want to hit those limits.
@@benssolarandbattery A BMS for solar should have separate paths for charge and discharge so charging can be stopped while Load can still be supplied. Also if used as you mentioned that absorption and float charge will still degrade the battery as Lithium batteries do not like that. This type of BMS is designed for applications where you only charge or only discharge not both at the same time like for example in a power tool or for an e-Bike (tho this sort of BMS for an eBike will be a bad idea as you need warning before motor cuts off).
@@DannyBokma Ben is pretty much on the money, see my longer comment.
I fully agree, on the other hand, you may leave charger in Li-Ion mode by accident or short battery by accident. LFPs are relatively save, but shorting LiPo by accident is serious hazard.
Batrium is expensive, but that would be my first choice of a good BMS. Daly programmable BMS, coming directly from the company you purchase the batteries from is my second option. Other BMS are not available to me in Pakistan, so didn't bother looking at them. Most people on different forums often go for "budget" builds. My issue is that with budget builds, there are greater chances of failures happening that can ruin the inverter or the batteries. Both expensive items. If you are still short by $300~$1,200 dollars to get bms, wires, circuit breakers. Than wait for the money and get good items. Once the system is setup, no one really goes and checked it every few days, much less every few hours after a few months.
At the top of the charge, there is a nearly 5% cross of the threshold. At the discharge, there is a nearly 11.5% cross. Thank you for the videos.
I like what you wrote, agree about BMS, it's a really important component in a system.
Batrium balance at best at 2amp isn't it?
@@shinosg-wiz4619 scroll down to balancing power, support.batrium.com/article/127-watchmon-comparison456
Depending on which model you get, you get different rates. In larger systems, it takes longer to balance. The balancing is done passively. You don't need massive amounts of amps to keep on flowing to balance. You just need to do it with small charge over time. I am not knowledgeable enough at the moment to recommend one system over the other or their pros and cons in specific details. I prefer batrium if you are looking to expand your battery backup in the future. If you want to keep the same setup for a few years to come, I prefer Daly bms. I have not used any bms so far, but hope, this is just my opinion on the matter.
@@asderven thank you for the link. Yeah I remembered right. At best 2.2ah. Batrium is made for serious cells (or for those with a good budget lol!) Not for these blue ones because these have generally bigger differences between them compared to way more expensive cells made in Europe.
@@shinosg-wiz4619 blue cells = LiFePo4 cells with aluminum casing. The older ones had harder plastic casing like the winston cells. The blue ones are smaller in size relatively and weigh less as well. As for the quality, if you buy them from a good seller, the blue cells are amazing. Most of these are produced in China, most people just resell them by putting on their own logo at times.
If you check out the forums at second life storage, people have tested all kinds of cells quite well. You can read their reviews to make up your mind as well.
Glad to help.
I think you’re trying to theorize the use of the BMS differently. The BMS upper and lower voltage cutoffs is to be there as a fail safe. If you are daily charging and discharging the battery to the point the BMS is kicking in, you’ve got your system setup wrong. The charger and inverter should do the limiting and should be set accordingly.
Usually, this kind of BMS used in inexpensive solar systems, where the load side represented as a simple 12V DC-AC inverter, in this kind of inverters user cannot set low cutoff voltage. Anyway, recorded a video just to let people know what to expect from BMS.
Below 2.0 vdc and above 4.2 vdc damages Lifepo4 cells. For that person that would buy the cheapest BMS, probably bought Grade G cells too, so it’s good enough. Thanks for video.
After having similar experiences with some cheap BMS modules, the only ones I use are programmable. It is not worth the risk. As far as balancing, I have mine on a monthly timer rather than continuous balancing. Good video. Thank you!
which one are you using?
@@SolarEngineering Hi, I've use several different types, depending on the pack makeup. I stick to the lipo4. With a 48 volt pack, I like this one. www.ebay.com/itm/2A-Bluetooth-Balancer-Li-ion-Lipo-Lifepo4-LTO-Battery-Active-Equalizer-2-24S-BMS-/124047924872?_trksid=p2349624.m46890.l49292. Sometimes I will not use the BMS and build a simple circuit that I can set precisely and depend. I don't trust these physically small BMS units that say 100 or 200 amps.
It is always good to keep an eye out for new things on the market though.
@@wearemilesfromnowhere4630 I like this balancer a lot, I'm using the same in my bigger battery bank.
Very good test! Cheap BMS, maybe even some expensive BMS. To buy one, look for one that can adjust under and over voltage adjustment per cell.
I'm using chargery BMS for my solar setup, but it has some issues as well..
thanks for feedback.
@@SolarEngineering Take some time and look into "Electrodacus BMS" Highly customizable but not from the beginners
@@georgedemean2228 thanks, going to check. I'm going to switch BMS in future, want to do right choice at this time
@@georgedemean2228 My understanding is that electrodacus doesn't make a 16s BMS.
@@mrrewog You are right, up to 8 cells (24V) but it's probably the most comprehensive BMS ever at that...
If a board with B-, C- and P- pins, can you connect such as symmetrical, charging and load in parallel together only on C-? BMS hx-4s-f100a bms
I have same question
For those using this kinds of BMS, I think it will be fine since its doing its job charging the batteries, it's just the fact that their high and low voltage cutoff is too high and low, well I think the protection they offer is supposedly the last resort protection. What I mean is you need to add a dedicated overcharge and over discharge module to make sure your batteries are safe, and in case any of that fails, then this is where this cheap BMS will be useful, at least they will disconnect your battery at some point😅 not to points where those expensive BMS can do better. But for a less budget, this things works!!
BMS is a last stand safeguard. Ideally it never gets called upon to limit discharge or max charge. The BMS only option is to open connection to inverter/charger which prevents damage but leaves you in a situation that must be resolved manually.
However, a charger only limits to overall cell pack voltage so if there is some cell imbalance, one cell may go over voltage during chargng unless BMS detect it and trips off.
You should avoid cheap BMS's that do not have adjustable max and min cell supervisory trip voltage adjusment. Cheap BMS's are typically fixed with a poor tolerance or even for wrong type cells like LiPo which have higher overcharge trip voltage points.
Another big defiiciency is maximum discharge or charge current claims, even on more expensive BMS's. For competitive reasons they often spec short term surge current as their current rating. It is not uncommon for BMS to only handle a continuous discharge current of less then half their claimed current rating. The MOSFET disconnect devices series resistance may be too high resulting in overheating. Lower series resistance MOSFET switches cost more.
Also to be careful of is voltage rating of the BMS for the number series connected cells in the battery array. A 4 cell LiFePO4, '12v' battery should have >20v rated MOSFET cutout switch devices. An eight cell '24v battery should have >30v rated MOSFET switch. A sixteen cell '48v' battery should have >60v rated MOSFET switches. The higher the voltage rating of the MOSFET, for a given series resistance device, the more expensive the MOSFET's are.
Low cost 12v self-contained LiFePO4 batteries with intenal BMS often are built with only 20-25v MOSFET's. These are not suitable for series stacking to make 24v or 48v array. Check with manufacturers spec to see what their maximum series stacking capability is. It manf. spec does not state maximum stacking then they likely are not suitable to series stackng batteries. For example, BattleBorn states they are four battery stackable to achieve a 48v system array.
Thanks for the information, agree with you about BMS role in solar system setup.
Use only the flat part of the curve and enjoy battery for long time
+1
I bought those same batteries from battery hookup. They were all mismatched when I got them. I wired them together in parallel for 2 days to equalize them. Which it seemed to. Then I ran them in series with a Daly bms. The batteries all went back to being unequal. So now I'm waiting for a charger that will top balance them. I hope it will solve the problem. The 40 amp Daly bms does not allow the battery pack to get anywhere near full charge. It's a 12s battery. It should charge to 43v . The bms won't let it charge past 40v.
In addition to what Roland W. said, one has to understand that the LFP is not like a simple bucket that when it first overflows it is full or first seems empty is actually empty. LFP is more like a sponge (or a Resistance/Capacitance network). As I am sure you have noticed in your many excellent experiments, if you charge an LFP to 3.65 volts and then come back some time latter (the longer the better) you will no longer be at 3.65 but, instead, well below it. Likewise, when you reach 2.5 and disconnect, come back later and you will be above 2.5 volts. When the manufacturer specifies 2.5 to 3.65 volts for capacity testing, they mean that one should really have a constant 3.65 and 2.5. True, there is not much charge in these regions but if one expects to duplicate the manufacturer's data one has to follow the same procedure. In any case, the internal resistance of the battery prevents the instantaneous flow of charge throughout the battery so it takes time for the charge to dissipate into the entire battery. The voltage you read at the terminals is localized until the battery has had a chance to reach equilibrium. A BMS which can be set to at a given value to disconnect and reconnect at another value can be set to repeatedly charge (or discharge) the battery until it finally approximates a true 3.65 or 2.5 volts. Your cheap BMS in this video apparently can't do this but, as you know, the chargery BMS's you also have can. Frankly, I really wouldn't worry about your BMS cutting off high as the battery is not entirely at this value, just the area local to the terminals. The lower cutoff voltage seems a bit low but that is just me getting paranoid rather than actual data on the matter. In any case, as Roland said, you are not relying on the BMS to handle everyday affairs but rather the solar charge controller or the inverter. Thus, I think the BMS in the video is probably okay to use if all you need is a bare bones BMS.
that's interesting, I thought 3.65-2.5 are hard voltage limits, but looks like it's not. Thanks for the information, I'm still learning.
@@SolarEngineering Admittedly it is confusing and their are plenty of folks out there who say NEVER go above 3.65 or below 2.5. Looking at Victron's website, they say a high of 4.2 volts and a low of 2.5. As Roland remarked, I have seen others who say the low end is 2 volts. I screwed up on a charge cycle the other day and hit more than 4.2 volts for probably 20 minutes or so and my battery still gave me full capacity on discharge (once I noticed my screw up I immediately put a resistor between the terminals and got down to 3.65 volts). In any case, I am trying to do a lot more research on the battery chemistry so I can try and improve the performance of my system as I seem to have batteries that were never matched. Although they are near spec when I test them one at a time, in combination I only get about 70% of the capacity I should. That is probably due to differences in internal resistance. As you may know, the latest rev of the chargery BMS firmware gives us an estimate of internal resistance but I don't know how accurate it is.
@@SolarEngineering There is actually a very good presentation on the intricate details of lifepo batteries on youtube at ruclips.net/video/QlDd3jkcxoQ/видео.html
Mind you it is quite technical. The presenter says that lifepo batteries actually handle overcharge very well but when they do start to fall apart is around 4.3 or 4.4 volts where the electrolyte starts to fail. Mind you, it does not happen all at once. The presenter also said LiFePo batteries are not that sensitive to low end voltage either and mentioned keeping cells above one or two volts.
Another good article is found here:
www.solacity.com/how-to-keep-lifepo4-lithium-ion-batteries-happy/
This article says 2 volts for the low end cut off and 4.2 for the high end. What is clear from all this is that it is not like falling off of a cliff. You do have a fair amount of wiggle room and even blowing it usually will not destroy your batteries in one big boom. At equilibrium I think a safe range that will give you long battery life is say 3.05 volts on the low cutoff and 3.38 volts or so for the high cutoff. Those are the voltages I'd like after the batteries sit for a while. I'll know more after a lot of painful additional testing.
On other interesting factoid for you. My first batteries were 12 volt (4s) lifepo but I made them from 8 cells with 4 groups of two cells in parallel. I think this is similar to what you have except you have 3 cells in parallel and, of course, you are at 48 volts. What threw me for a loop is that I was only getting 70 - 75% of the capacity I should have gotten. I tried lots of different batteries and moved them around (so one might have been the first cell in one case and the third in another) and I just was not getting what I expected capacity wise. So I blamed the batteries. Then I took several individual cells and tested them by themselves and got around 95% capacity. So then I built a 12 volt battery with 4 individual cells so I had none in parallel and, VIOLA!, I got 96% of the capacity I expected! So there is something about putting the cells in parallel that was causing degraded performance. When I did the parallel experiments I had each group of two parallel cells connected to the next group via one bus bar. However, I have seen recommendations that each group of parallel cells should have a busbar per cell connecting to the next group. So, in my case, my two positives in parallel would each have a bar to the two negatives in parallel in the next group. One might think this is overkill, but I calculated that the busbar resistance is about 25% as much as the cells internal resistance so, MAYBE, I need to repeat the experiment with the parallel cell groups connected to the next group with two busbars. OR, maybe the huge differential voltages I saw (250 - 300 millivolts) at the end of discharge were due to some other weird cell chemistry effect that highly favored one cell in a parallel group over another. Anyway, that difference vanished down to something like 30 millivolts when I took my cells out of parallel configuration. Maybe you can run some tests and see what you get?
@@robertgrant5895 somehow I missed your post. I'm going to check that video. And curious about paralleled cells. Thanks for detailed info.
Pleaese check the BMS spec, it does state the overcharge detect is 3.75V and overdischarger detect is 2.10v. both working exactly as spec in the video.
Clearly, he did not read the manual ...
It works but the values are too stupid.
I think you get it differently sir. The BMS cutoff charging will be higher because when you charge, the voltage will be lifted up. For how much is depending on how fast you charge relative to C rate. Faster charging, higher voltage lift.
Also you can find datasheet of any BMS on the internet or from the seller. I hope you understand.
Those boards may contain only a balancer and eventually short circuit protection, not necessarily under/overvoltage protection. From what I saw most of them are JUST balancers. Yeah, always check if they are what you want them to be.
This board does have both Over-Voltage Protection and Under-Voltage. Trying watching the video ...
I have a 12V 100Ah LiFePo4 (internal BMS) driving my boat motor and stupidly just connected a 300W solar panel directly to it. I assumed the BMS would prevent overcharge, and it actually worked fine for several months until I made a long trip and fully discharged it. Since then I can't get it to charge, even though the voltage is 14V. Any idea what happened?
Noticing you are using a discharge graph, if you use a charging voltage graph you would get different results. The open circuit voltage is always different than the measured voltage with large current in/out from the battery.
For longer life till what voltage should we charge a LifePo4 cell before storing it long term?
Those voltages are not going to damage the cells to any real extent with LiFePO4. You can actually charge them to a max of 4.2 and a minimum voltage of 2.0v. It's just that you only have about 1% capacity from 3.5 to 4.2v on the top end and only about 1% capacity from 2.5-2v on the bottom end. 3.7 to 2.3 is going to give you around 98-99% of the maximum capacity of the cell. For long-term solar energy storage staying between 3.45 and 2.8 is a good idea but you should not be relying on the BMS to cut power as the charge controller and inverter should be shutting down before the BMS ever reaches the cutoff voltage. Also as you said, if you are building a large battery bank you should be investing in decent components throughout the entire system.
Hi there, didn't know that LiFePo4 could be charged up to 4.2V, in every spec I just saw 3.6V
Agree on BMS responsibility, for me ideal BMS is a BMS that could be configured low/high voltage disconnect. And it should control charge and discharge with relays, I'm using chargery BMS, but it's far from ideal.
I follow 2.6 to 3.5v.
Thats where is meat of capacity is without Needlessly stressing the cells.
@@jec_ecart That is a good cycle to follow, LiFePO4 cells will saturate at 3.5V (actually a little less and no reason to push them harder than needed in most storage conditions) if left long enough but it just takes longer than charging them to 3.65. I generally don't take my cells much below 3.15v since I try to keep them off the bottom of the charge curve so I always have a reserve but 2.6 isn't going to hurt them as long as they are recharged in a timely fashion. We must always remember that calendar aging is going to affect the life of the cells far more than cycling for anyone charging once a day or less.
Which BMS model is that? I'll definitely avoid it.
How about if you have MPPT-type solar charger, there is own limits to the charging max and load cutoff. I think they need to be set first (e.g. 14.6V/10V), and then, if those fails, BMS comes to help you, to protect your batteries againts total disaster. Your cheap BMS in video seems to work correctly if thinking like that. What you think?
you are right with the voltages setup, but still, BMS should be in a range of voltage accepted by the battery.
here is the video about my system settings: ruclips.net/video/gFwz2uFpEHE/видео.html
Great excellent vid again thank you👍
Im wondering if we can just replace resistors which sets the limits of them are programmed into IC
I think it's totally possible. Personally I would pay few extra $ and get something programmable, like this one for example:
ruclips.net/video/k8Wkg-tVnx8/видео.html
Have you looked at the Electrodacus BMS? Open source, very transparent dev, much goodwill from the community.
yeah, I checked Electrodacus, for me, it's not going to work because this BMS only supports up to 8 cells, in my case I have a 16s system. But in general, it looks like good quality BMS.
I'm using chargery BMS at this time, but quality is questionable.
I just got another BMS (check the latest video), haven't fully tested it yet, but looks promising for small and mid systems.
Still in search of good BMS for bigger systems (20kWh+).
@@SolarEngineering I took the liberty of e-mailing them to ask on the above. If there's an answer I'll send it your way. Onward and upward! :)
Thank you sir.
Спасибо за видос! Весьма информативно!
спасибо за отзыв
I was thinking, not sure whom to ask. What if we get 280ah 12V system. What kind of things will we need to make it work with a desktop? A BMS. I want the batteries to provide power to the desktop 24/7, and get charged by the electricity coming out the wall socket (220V ac, there is a solar on the roof, but the wiring will be painful to bring down from 2~3 floors). When the batteries reach a certain low point, they will start charging up slowly. My desktop usually takes 40W~100W. I don't play games right now or edit videos. In future it will be taking 400W~700W.
The main purpose is to stop voltage fluctuations from affecting the power supply. To stop sudden power loss to cause any damage to the pc, or when the electricity comes back.
You'll need 12v280AH pack + BMS, then 12v charger (AC-DC) and 12v DC-AC inverter.
I don't know your exact application, but I think something like UPS will work better, because you'll use AC grid power when it's available and DC only when AC grid power is off.
@@SolarEngineering I want to run my computer from the batteries 24/7 (uploading, rendering, number crunching). Computers usually have 12V dc power supplies. I just need something to keep the batteries charged up.
I was thinking when batteries hit 3V/cell, they start charging at 0.1C~0.2C (set in the inverter), and when it hits 3.5V/cell, it disconnects. The computer drawing electricity is usually quite low. This way the computer is protected. UPS have sine wave issues that I want to avoid, and the UPS I get here are usually with no settings other than factory settings.
@@asderven just to double check, you want to connect computer directly to batteries without an inverter? Also is it laptop or stationary PC?
@@SolarEngineering stationary pc, batteries with an inverter. I was thinking, I just need a 2KW inverter for the 1,600 watt power supply, and set it up like I would with a solar system and use a bms as well as surge protectors.
Sir, can you please answer me following questions
1. what is 1C charge rate & 3C discharge rate?
2. I have 12ah lifep04 battery pack with 4s 30Amp bms, so will that bms damage my cells with high current ?
1C rating means that full discharge of the cell from full to empty is going to happen in 1 hour.
So on your example of 12Ah pack - 1C rating is going to be 12Amps. (If you pull 12 Amps constant load from pack, it will take 1 hour to discharge it).
Formula: C rating = charge(discharge) current / pack capacity in Ah. (Example: 0.2C rating = 2.4A / 12Ah )
Coming back to your questions:
1. 1C = 12A, 3C = 36A
2. BMS is not regulating Amperage going in/from the pack, it's just protecting if the current is too high (some BMS has settings, some programmed from a factory). BMS that we see in this video doesn't have that form of protection, BMS will just melt trying to pass current.
The second form of protection is low/high cell voltage, BMS will sense voltage on every cell and if it's over limits, then it will disconnect pack from charge (or load). In the video, we see that high voltage disconnect is too high (3.75V), and if you just going to rely on BMS to protect pack from overcharging, then pack will slowly degrade due to constant overcharge. To answer you 2nd question in short: no BMS will not damage your cells because it's not setting amperage in./out, inverter and charge controller will damage cells if you are going to push it over limits.
@@SolarEngineering
Why charge controller will damage cells?
As we have bms right? won't it protect cells?
I have 20amp mppt charge controller
@@ankamanirudh8837 I answered your question: "will that bms damage my cells with high current"
If you are planning to push more than 1C while charging your cells - it will wear pack faster. Please check cells specification about the max current you can charge it.
to get more accurate answer, you need to provide all details about cells manufacture, charger, inverter, load that you are planning to apply.
@@SolarEngineering
So, if incomming current from charge controller was 15amp then bms can easily transfer it to cells right? So, this flow will damage my cells right?
So should I need to increase my battery pack to 18ah so that charging current it will be in limits right?
Looks like I should build a "test" battery, perhaps using capacitors for cells, so I can test the BMS without damaging real battery cells, or taking such a long time to charge and discharge.
I recently got another BMS (check latest video on the channel), this BMS looks promising, going to test it soon.
Hopefully, this BMS will work as expected, then you don't need to build a test battery.
The harm in a cycle or two is miniscule. According to Wikipedia, they last from 2 2000 to 20 000 cycles. I will assume the biggest factor is how they're used. A full range daily cycle would suggest four to five years, at a minimum, unless you are treating them really badly.
I suggest that if you are doing full cycles daily, then you should double or treble the number of strings, that automatically reduces the DoD.
I would hope that the solar regulator prevents over charging, that the capacity of the battery presents excessive discharging, and that the choice of matched batteries largely keeps them balanced, leaving the BMS not much to do.
Hi dear thanks for your video
Plz what your opinion about battery lishen lifepo4 3.2v
And basen lifepo4 3.2
These companies are good ???
Hi, I haven't tested these brands.
what is the name of step up converter used in this video. Thanks, Frank
Hi Frank, it's bench power supply: amzn.to/3jqhCCH
Hi, greetings from Spain. I just have a couple of questions regarding how to charge the LifePO4 battery, I want to build a 12v 100Ah portable battery that will be charged only from 220 ac, I will not be using solar panels for charging. In that case I do not need a MPPT, Can I charge the battery just with a cheap PWM made in China and a 12v power supply from a PC.
yes you can, but I would recommend to get just 12V charger or power supply (15V actually).
Hello everyone, the cheap bms combined from cheap elements like Ic Dw01a that cause damaged your battery
The bms is ok. A bms is a protection device and is not meant to be used to charge and discharge the batteries. For example, in a solar system, the solar charge controller is the battery charging device and should be configured to stop charging at an appropriate voltage. For a LiFePO4 battery, I'd recommend no more than 3.5v per cell. For discharging, that is usually an AC inverter and they usually shutoff at about 2.65V per cell.
Does that mean this bms is working within the specs?
IMO 3.65V cutoff would be within lifepo4 specs.
This means that it is still in accordance with Lifepo4 specifications?
@@mohamadirfanabdullah5913 I'm not getting your question. Lifepo4 max charging voltage 3.65V per cell. This particular BMS states that it will allow charging up to 14.4V, but it definitely failed.
@@SolarEngineering Who told you that this BMS must cut-off at 3.65 volts? Did you read the manual or *NOT* ? The manual states Over-Voltage cut-off at 3.75 Volts !
@@MrSummitville pause video on 0:06, look at BMS sticker voltages and divide it by 4. Simple.
Again, feel free to ignore this video and use this BMS.
The big problem with lifepo4 battery Cells is that they need an active balancer board with higher amperage than the charging or discharging amperage.
I have the exact same BMS I purchased just to protect cells while charging. It did NOT work. Thank God I was monitoring with a Battgo. I noticed one cell hit 3.7V, and I immediately diaconnected the charger. That BMS does not work. Pure garbage and waste of money.
Did you read the manual? It states ... Over-Voltage is at 3.75 volts.
3.75 is far too high. Why even have a bms then?
OMG, that does make sense, 10k battery with $35 bms, that's a nono
I think a lot of DIY LIFEPO4 users do NOT need a BMS , as long as you stay within the upper and lower " knees" of the charging curve , so for a 12 volt ( 4 cell) LiFEpo4 system that would be minimum voltage 12.6 volt an upper chance voltage 13.6 volt, nominal cell voltage is around 3.3 volt, I'm ve been running my 12 volt/ 200 ah solar system for 4 years now WITHOUT a BMS and ( after initial TOP balancing to 3.65 v per cell) the cells stay between those " knees" in perfect balance, so better No BMS than a cheap BMS, a low power cutoff is already in my inverter,and a rightly programmed solar charger keeps the upper voltage in check, wat IS important is to NEVER " FLOAT" LITHIUM, so after reaching the desired chance voltage( I'm using 13.6 volt/ 3.4 volt per cell) STOP CHARGING, could it be simpler?
You don't need a BMS, until that one day, when you do need a BMS ...
These no name Chinese bms are quite junk. Even if they work, the default low & high cuts are far too unsafe.
Выдаёт произношение что язык не родной. Похоже русский)))
можеш те саме але по нашому або по рус
. You have no idea what your talking about. A bms is the last line of defense as a safety feature for your battery. You just showed me that that is a good bms.
I'm glad that I helped you to discover good BMS :)